In one of the worst boating tragedies to occur on the Thames, 51 people, many in their 20s, died when the Marchioness collided with the dredger Bowbelle on 20 August 1989 - 25 years ago yesterday.

The tragedy occurred in the early hours of Sunday morning as both vessels neared Southwark Bridge. The Marchioness, a pleasure boat that had been hired by a Portuguese financier for his 26th birthday, had 131 partygoers on board when its upper deck was ripped off by the Bowbelle, a 1,880-tonne dredger that tore into its stern.

In the near pitch black conditions, the Marchioness overturned and sank. Of its 131 passengers, 80 survived the murky waters of the Thames.

With police confirming that there were no remaining survivors, the grim task of recovering bodies began. The captain and second mate of the Bowbelle were also arrested.

In the aftermath of the tragedy there were urgent calls for greater safety measures to prevent another disaster. As the owners of the Bowbelle came in for harsh criticism, they agreed to a £6m compensation package for the relatives of the victims.

What the families really wanted, however, was to know who was responsible for the fatal collison. Almost a year after the disaster, a leaked report by the Marine Accident Investigation Bureau put the blame on a look-out failure - the crew of the much larger Bowbelle were found to have not warned their captain that both boats were on a collision course.

In 1991, the captain of the Bowbelle, Douglas Henderson, was prosecuted twice for negligence, but was acquitted after two juries failed to reach a verdict. Unhappy with the outcome, the husband of one of the victims began a private prosecution against the owners of the Bowbelle. The case was dismissed a year later.

More disappointment for the families came in 1994 when an inquest into the disaster returned a verdict of unlawful killing, but in July 1996 the Crown Prosecution Service said there was insufficient evidence to justify any further criminal proceedings.

After campaigning for over 10 years, the victim's families got the public inquiry they wanted.